This invention relates to interferometers utilizing double-pass cat's-eye retroreflectors, and more particularly to an improvement in the drive of a continuous scan interferometer of the type shown in U.S. Pat. No. 3,809,481.
In an interferometer (interference spectrometer) of the double-pass type, a single fixed mirror is employed in the path of both split beams to cause them to double back through separate retroreflectors. Changes in length of one optical path relative to the other are achieved by linear displacement of one retroreflector using a motor driven lead screw for large, low frequency changes, a moving-coil actuator in the other optical path for smaller, midfrequency changes, and a piezoelectric actuator on at least one of the two optical paths for small, high frequency changes. An object of this invention is to simplify the scanning servo system and circuit design without degrading performance.